%C A136296 "Special augmented numbers" from Zak Seidov

[Maximilian Hasler]

As I said in reply to Frank's mail yesterday morning, divisors()
should be replaced by factor()[,1], i.e.,
to get these primes with d digits, use:

A136296d(k) = { local( d = factor(10^(k+1)+1)[,1] );
 if( d[#d]<10^(k-1), [], vecextract( d, if( d[#d-1]>10^(k-1),"-2..-1","-1"))~)

then:
for( k=1,99, print1(A136296d(k)))
[13][137][9091][][909091][5882353][][][][][][][][][][][909090909090909091][][][][][][][][][][][]
[909090909090909090909090909091][][][][][][][][][][][][][][][][][][][][][]
[9090909090909090909090909090909090909090909090909091][][][][][][][][][][][][][]
[909090909090909090909090909090909090909090909090909090909090909091][][][][]
  *** factor: user interrupt after 1mn, 4,828 ms.

PS: Oh, I just get Frank's reply with roughly the same code... well, a
bit different: it doesn't use the result that only the highest or
second highest divisor can be of needed length.